If I'm gonna leave my computers on and run up my electrical bill, then I want to at least feel like my computers are doing something useful, and to me, that's learning how genetics works and finding cures for disease, not brute force hacking on for a needle in a haystack.
Brute - alot of folks have come and gone here saying the same in a trolling type of manner... In about 99.9% of the case, I ignore them because they are trolling, but in your case, I'll respond since I am running multiple projects including RC5, OGR, AND both genome and folding (and as an FYI - my 56aa genome is uploading as I type this)...
RC5 appeals to many people, maybe not so much due to the goal of it, but to one's ability to get to that goal. That is, it stimulates the drive to tweek your hardware, and gain additional hardware, to get to "X" faster than anyone else. It's very much a psychological thing. The ease of the configuration of the client and the elegance of how it works and interacts with your hardware and software, is a programmer's and/or hardware freak's dream... It is truly a marvel in the distributed computing world as a model client. I consider dnet the ultimate computer hobbyist's project.
Running RC5 just these past 2 weeks, taught me how to setup a personal proxy to cache WUs as well as run a stats app against that data on a different machine. And the pproxy is running on x86 (dual Xeon) windud while my stats and web server reside on my alpha that is running Linux and the Apache web server. So running dnet for me has been educational as well as competitive.
SETI on the other hand, has the justification that people like Assimilator1 have mentioned - mainly, if you don't look, you won't find. No one can deny that SETI@Home set the standard for the later screen-saver based distributed computing projects like folding@home. Despite the doubled WU times, I still run SETI because it was the first distributed computing project that I had ever run.
Both Genome@home and Folding@home are also excellent projects, and I run them, however both projects are new and there is a whole potential audience out there behind firewalls or on intermittant dialup connections who can't run it. Fortunately, genome is solving the caching problem by allowing the client to do a dnet-like work around for machines that lack a net connection... Something that is almost akin to doing "randoms" in RC5, except that the set of amino acids downloaded in the particular WU that is used for caching purposes (ie., the WU that will be re-run over and over), would have a different "seed" added to it to cause a different gene to be created at the end of a re-run. Thus with the single WU, you can be offline for months and end up designing many many different genomes... And when you finally go to upload those genomes, all of them would count towards your stats.
Anyway, I think the bottom line is - people will run what they want to run. Period. I like alot of projects and run them.
Others will focus on and become #1 at the single project that they like.
It's their choice! 😉